How to childproof my iphone 5c?

My wife and I recently got our son an iphone 5c for his birthday. We did all the basic restriction things such as blocking the app store, and adult content, etc. Etc. Etc. However, there's something else bothering me, we're a bit paranoid about strangers being able to call his number. Is there a way to black All numbers from being able to call or text his number EXCEPT for a few select phone numbers?

Please let me know what you guys can come up with.

You could look for an app on the App Store that does something like that.So, you'll need to lift the restriction on the App Store to do that then put it back on when you're done.
Just one thing: do not block Facebook or Youtube. Doing that is like opening Pandora's Box.